In a large nonstick skillet, heat 1 tablespoon vegetable oil over medium-high heat. Halve 3 bananas lengthwise and add to the pan cut side down. Cook until deep golden, 2 to 3 minutes; transfer to a cutting board and cut into bite-size pieces. Wipe out the skillet and heat another tablespoon vegetable oil. Season 3/4 pound skinless, boneless chicken thighs with salt and pepper; add to the skillet and cook until browned and cooked through, about 8 minutes. Transfer to a cutting board to cool slightly before thinly slicing. Lower the heat to medium, add 3/4 cup thinly sliced scallion whites and cook, stirring, until golden, about 3 minutes. Add 2 finely chopped serrano chiles and cook, stirring, for 1 minute. Stir in 3 cups cooked and cooled white rice, increase the heat to high and cook, stirring occasionally, until the rice begins to toast, about 3 minutes. Remove from the heat and stir in the banana, chicken, 3/4 cup thinly sliced scallion greens and 2 teaspoons soy sauce. Sprinkle with chopped salted peanuts.